mayflies

n. [ Many, adj. + plies, pl. of ply a fold. ] (Anat.) The third division, or that between the reticulum, or honeycomb stomach, and the abomasum, or rennet stomach, in the stomach of ruminants; the omasum; the psalterium. So called from the numerous folds in its mucous membrane. See Illust of Ruminant. [ 1913 Webster ]